1. Field of the invention
This invention relates to a constituent member for electrical or electronic devices, particularly a surface treated metal member utilizable as the substrate for a photoconductive member such as electrophotographic photosensitive member, etc., a method for preparing the same and a photoconductive member by use of the surface treated metal member.
2. Related Background Art
The surface of a metal member is applied with various cutting or grinding working in order to impart a surface shape corresponding to the use.
For example, as the substrate (support) for a photoconductive member such as electrophotographic photosensitive member, etc., a metal member shaped in plate, cylinder, endless belt, etc., is used and, for formation of a photoconductive layer, etc., on the support, its surface is finished such as by mirror-finishing, cutting working, etc., for example, by diamond bit cutting with the use of a lathe, a milling machine, etc., and it is worked to a flatness within a predetermined range or, in some cases, finished to an uneven surface with a predetermined shape or any desired shape for prevention of interference fringe.
When such a surface is formed by cutting, the bit may come against fine intervening matters such as rigid alloy components, oxide, etc., or blisters existing near the surface of the metal member, whereby inconveniences may occur such that workability of cutting is lowered and also the surface defects caused by the intervening matters, etc., are liable to appear by cutting. For example, when an aluminum alloy is used as the metal member to be used for the support, there exist in the aluminum structure hard intervening matters such as intermetallic compounds of Si-Al-Fe type, Fe-Al type, TiB.sub.2, etc., and oxides of Al, Mg, Ti, Si, Fe and blisters due to H.sub.2 and at the same time also there occur the surface defect such as grain boundary stepped difference arising between the adjacent Al structures with different crystallization orientations. When, for example, an electrophotographic photosensitive member is constituted of a support having such a surface defect, uniformity in film formation becomes worse, leading further to impairment of uniformity in electrical, optical and photoconductive characteristics, whereby no beautiful image can be provided and the photosensitive member becomes practically useless.
Also, according to cutting, there will ensue other problems such as generation of cutting powder or consumption of cutting oil, cumbersomeness in disposal of cutting powder, treatment of the cutting oil remaining on the cut surface, etc.
As an alternative method to control flatness or surface coarseness of the surface of a metal member, means to cause plastic deformation such as sand blasting or shot blasting have been practiced but it is not possible to control accurately the shape, precision, etc., of the unevenness imparted onto the surface of the metal member.
On the other hand, as the material for a photoconductive layer, various organic or inorganic photoconductive substances have been employed. For example, an amorphous silicon having its dangling bonds modified with monovalent elements such as hydrogen or halogen (hereinafter called a-Si(H,X)) is often employed as the material for a photoconductive layer due to its excellent photoconductivity, frictional resistance and heat resistance. For making this a-Si(H,X) practically useful, it is required to be constituted of multiple layers depending on the proposed use and may include a charge injection preventing layer which prevents injection of charges from the support, a surface protective layer such as SiN.sub.X, SiC.sub.X, etc., in addition to the photoconductive layer of a-Si(H,X). Also, the uniformity in the photoconductive member is very important and, if there exist nonuniformity in the photoconductive characteristics due to a defect such as pinholes, not only can beautiful images not be provided, but also the photoconductive member becomes practically useless.
Particularly, it has been known that the form of the film of a-Si(H,X) is greatly influenced by the surface shape of the support. Above all, in an electrophotographic photosensitive drum with a large area for which substantially uniform photoconductive characteristics are required in most portions, the surface condition of the support is very important. Presence of a defect on the support surface will decrease the uniformity of the film so as to form pillar-shaped structures or spherical projections, whereby nonuniformity in photoconductivity may be caused.
Accordingly, when employing a tubular material (cylinder), etc., of an aluminum alloy as the support, various precise cutting or grinding working such as mirror finishing, emboss finishing, etc., are applied on its surface. During such a process, the so-called intergranular stepped difference may be created due to the difference in deformation and restoration by the stress received during working because of the difference in crystal orientation among various kinds of crystal grains sectioned by grain boundaries, whereby defective portions may be formed on the cylinder surface. For example, unevenness with a depth of about 100 to 1000 .ANG. may be formed on the cylinder surface, or alternatively defects such as cracks may be formed along the grain boundaries to generate numerous pillar-shaped structures or cone-shaped spherical projections on the grain boundaries, whereby photoconductive nonuniformity or abnormality in photoconductive characteristic will be increased. Further, crystal grains with greater sizes can poorly disperse the stress created during working with the result that a greater grain boundary stepped difference will be created.
Further, in the process of applying various cutting or grinding working as described above, if there exists a hard portion, called a hard spot, due to various intervening matters as described above, in the mirror finishing process such as by cutting working, it becomes a cutting resistance against the cutting bit to cause formation of a defective portion on the surface of the aluminum cylinder, thus resulting in generation of cracks of about 1 to 10 .mu.m, gouge-like scars, further fine unevenness, or streak-shaped flaws.
However, in the prior art in order to minimize intervening matters or blisters due to H.sub.2 gas, it has been required to use an aluminum alloy base material applied with various countermeasures. Therefore, addition of working steps and increase of cost caused by application of these countermeasures could not be avoided.
Further, electrophotographic photosensitive members receive sliding friction repeatedly with a blade, fur brush, etc., for removal of residual toner. During this operation, durability of the photosensitive member can be improved by increasing the hardness of the support simultaneously with improving the abrasion resistance of the surface of the photoconductive layer, and there was an example in which a high hardness Al material, etc., was used (for example, Japanese Laid-open Patent Application No. 111046/1981). However, as mentioned previously, particularly in an a-Si photosensitive member there was involved a problem by the precipitate in the Al structure, which is particularly marked in a highly concentrated Si type Al alloy.